The current London mayor, Boris Johnson, has been slow to face up to the challenge. His tenure began by removing the western extension to the Congestion Charging Zone, thus increasing vehicle numbers in Inner West London, and opting out of using the Congestion Charge to tax the most polluting vehicles. This would have boosted the adoption of hybrid and electric vehicles (still only a meagre 1% of new cars) and reduced heavy emitters in Central London. Furthermore Johnson has not succeeded in comprehensively upgrading London’s bus and taxi fleet to hybrid and electric vehicles, instead embarking on an expensive new Routemaster project which still produces substantial emissions and currently makes up a minority of the overwhelmingly diesel bus fleet.

NO2 Annual concentration in London 2010, modelled by the London Atmospheric Emissions Inventory. All of Inner London and many major roads in Outer London greatly exceed the EU limit.

Looking to the future, London must now tackle the air pollution problem with a new mayor in the upcoming 2016 elections. The scope for change looks positive, as the main candidates on both the left and right have been openly discussing the need for change. What then could a new mayor do to address air quality and improve the health of Londoners?

Pricing Out Polluting Vehicles with the Ultra Low Emission Zone
To be fair to Boris Johnson, he did finally respond to pressure and announce a significant air pollution policy in 2013, dubbed the ‘Ultra-Low Emissions Zone‘. The ULEZ is set to come into effect in 2020 and essentially uses the Congestion Charging infrastructure to tackle the most polluting vehicles (similar to what Livingstone proposed way back in 2006). The question is whether the ULEZ goes far enough. It’s based on Euro emission standards, which measure NO2 and PM10/2.5 as well as CO2 emissions. It correctly targets diesel vehicles, requiring them to meet the Euro 6 standard, which only came into force in September 2015, so almost all current diesels on the road would have to change or pay the charge. This means that the main source of NO2 emissions will be appropriately targeted.

The current Congestion Charge boundary will be the basis of the Ultra Low Emissions Zone (map by TfL).

There are limitations however. The charge is only going to be £11.50 (except for large buses and HGVs), so it likely many diesel users will continue to drive into Central London and pay the charge. Furthermore the ULEZ will only affect Central London; the rules on diesel taxis and private hire vehicles have not been decided; and ULEZ zone residents get an overly generous exemption until 2023.

The next mayor will have a number of options that could be pursued if they want to be bolder than Johnson’s ULEZ proposal. These include increasing the ULEZ charge and/or Congestion Charge, bringing the ULEZ implementation forward to an earlier date, and potentially reintroducing the Congestion Charge Western Extension. All of these would make significant improvements to air quality, but would be controversial with drivers, many of whom were mis-sold diesel vehicles in the past as a supposedly environmentally benign option. The mayor may also want to re-examine the wider Low Emission Zone (LEZ) that tackles very polluting vehicles entering the whole of Greater London, as this affects the entire city and has not changed since 2012.

Euston Road, one of London’s busiest and most polluted routes with NO2 annual concentrations typically twice the EU limit (photo by D Smith).

Banning Diesel?A more radical approach currently being proposed for Paris is to ban diesel cars all together. This would certainly make a huge improvement to air quality. The problem for London would be that the city’s bus and taxi fleet would fail this restriction, and there would likely be a backlash from thousands of car and van drivers. This would be a very confrontational approach for a new mayor.

The more pragmatic solution for London would be to work with the ULEZ framework, considering stricter measures and higher charges, and implementing the policy earlier. One very important issue for the new mayor is emerging from the current Volkswagen emissions scandal. It looks like the latest Euro 6 diesels produce significantly higher NO2 emissions in real world driving conditions compared to the misleading testing conditions. If this is the case then the proposed ULEZ will be much less effective in improving air quality (as Euro 6 diesels will be exempt from the charge). The ULEZ may have to charge all diesel vehicles, regardless of their Euro rating. This decision would need to made very early, so that there is sufficient time for car users to adjust behaviours accordingly.

Pedestrianising Streets and Upgrading the Bus FleetOxford Street is London’s busiest pedestrian street and has some of the worst NO2 pollution in Europe. A response that is gaining popularity is to pedestrianise the whole street. Certainly this would be an iconic change to both the image of London, and to the experience of the city for thousands of Londoners and tourists. The challenge for this measure is avoiding creating bus jams at either end of Oxford Street, and handling the extra demand levels that would be placed on the already congested Central Line. These challenges are not necessarily permanent however, as the arrival of Crossrail in 2018 (which follows the west to east Central Line route through Inner London) has been described as a ‘game changer’ that makes pedestrianising Oxford Street a realistic option. The new mayor should certainly pursue this possibility.

The wider challenge for the mayor is not to just think about Oxford Street, but to accelerate the upgrading of the entire bus and taxi fleet towards zero emission vehicles and develop wider pedestrianisation policies. This would improve air quality for all of London’s high streets. London is still at the trial stage of pure electric double-decker buses, which represents disappointingly slow progress considering how long we have known about air pollution problems. There’s been better progress on electric/hydrogen single-deckers. Considerable investment will be needed to upgrade the bus fleet, with decision-making based on real evidence and value-for-money. Johnson’s Routemaster project has failed both these criteria, and better leadership is now required.

Heathrow Third RunwayAll the main candidates for the London Mayor oppose the expansion of Heathrow, with air pollution alongside noise pollution amongst the most important factors. You can see how Heathrow already dramatically increases emissions in West London in the NO2 annual concentration map at the top of this article using the London Atmospheric Emissions Inventory data. This is due both to emissions for aircraft engines, and the thousands of cars driving to and from Heathrow everyday. The challenge will be how effectively the new mayor can challenge the UK government to reject the Heathrow expansion option.

Overall, the issue of air pollution has gained unprecedented prominence as we approach the 2016 mayoral elections. The main candidates need to respond accordingly in their manifesto commitments, with London having a lot of catching up to do after eight years of little change. It will be interesting to see which candidates are prepared to be bolder.

Household energy use is a key indicator for understanding urban sustainability and fuel poverty, and is a timely topic now that winter has arrived. The LuminoCity3D site maps domestic energy use in England and Wales at 1km2 scale using data from DECC. This map has also just been published as a featured graphic in Regional Studies Regional Science. The household energy use distribution is really fascinating, with large scale regional variation and fine scale intra-urban patterns identifiable-

Average domestic energy use 2012, click to view interactive map

The lowest energy use per-household is found in cities and towns in the South-West region such as Plymouth and Exeter, and also along the South coast. While the highest energy use per-household is found in commuter belt towns around London. The variation within city-regions is very high, with for example London and Manchester averages varying by up to a factor of 5, from a mere 8kWh to over 40kWh per year.

The main drivers of energy use are generally housing type (more exposed walls=more energy use; larger house=more energy use), household size, wealth and climate. Often these factors are correlated at household and neighbourhood levels- so for example wealthier households in England and Wales are more likely to live in large detached houses, and these households tend to be clustered together. These trends produce the high energy use pattern seen in London’s commuter belt, as well as in the wealthier suburbs of other large cities like Birmingham, Manchester and Leeds. South West England on the other hand benefits from the mildest climate in the UK, has a relatively high proportions of flats and generally lower average household sizes, thus resulting in the lowest energy use.

We can see how these factors play out for London in the map below. The height of the hexagons shows density, with higher density areas clearly using less energy. City centre households have considerably lower energy use, with a strong bias towards Inner East London where incomes are lower.

London average domestic energy use 2012, click to view interactive map

Energy use areas correlate strongly with the most prevalent housing type map (also on the LuminoCity3D site), with flats and terraced housing the lowest energy users, and detached and semi-detached areas the highest.

The relationship with household size is less clear cut, but it can be seen that average household sizes are smaller in the city centre. On the other hand, areas with high average household sizes such as Stratford and Wembley, do not have particularly high average energy use.

London average household size 2011, click to view interactive map

Overall domestic energy use patterns tend to mirror transport sustainability, in that higher density city centre areas perform more efficiently compared to low density suburbs. On the other hand the link to city size (which tends to be strong in transport sustainability relationships, with bigger cities reducing car use) is much weaker, and the most efficient locations are often small and medium sized towns and cities. It is not clear in this analysis whether more recent green policies (such as improved insulation or CHP schemes) are having much effect, but several cities with green reputations like Brighton and Bristol are amongst the best performing cities.

Following rapid growth and a chronic lack of new development, housing affordability has reached crisis levels in London. Median house prices are at £300k (8 times median household income) while average prices have passed half a million. London is now amongst the most expensive cities in the world, a situation with severe consequences for economic competitiveness and for inequality. Rents continue to increase faster than wages, ownership is being restricted to affluent populations and the social housing waiting list now stands at 345,000 households, nearly double the figure from 15 years ago.

Recent development figures have been very low. London needs at least 50,000 new homes per year to meet demand, yet only 21,000 were built last financial year, and this figure has been below 20,000 for all of the last five years. Nationally around 200,000 houses a year are needed, and we are building around 100,000. These figures amount to a comprehensive failure of national and mayoral policy.

Clearly substantial changes are needed. Last week the Centre for Cities outlined how this change could happen, launching their ‘Building Change: Delivering Homes Where we Need Them‘ report. It convincingly argues that we are failing to deliver homes where demand in greatest- in the vicinity of rapidly growing towns and cities- resulting in spiralling housing costs.

The report makes a range of positive recommendations for enhancing local authority capacity in relation to delivering new housing, including the streamlining and reform of compulsory purchase orders for faster development and allowing cities to benefit from uplift values in land; allowing local authorities to borrow more with longer term commitments from central government; and enabling greater cooperation between local authorities to tackle city-region challenges. Best practice examples are provided from local authorities that have successfully delivered new housing, such as Bristol and Milton Keynes. The report also provides a useful summary on brownfield capacity, with for example the potential for 350,000 homes on brownfield sites within the GLA.

Releasing Greenbelt Land for Development
By far the most politically controversial aspect of the report is the recommendation to reconsider greenbelt development restrictions. Prioritising brownfield land has been a central foundation of compact city planning over the last twenty years, directing development towards inner city regeneration and away from rural areas. Yet brownfield land can be expensive to develop, and in combination with greenbelt restrictions, land prices have soared. These spiralling land costs have significantly curtailed new housing.

Opportunities for housing on ‘Usable Greenbelt Land’ around London are mapped in the report (figure below), based on locations within 2km of rail stations. The Centre for Cities estimate that there are opportunities for 430,000 housing units on greenbelt land within the GLA, and opportunities for a massive 3 million housing units on the London greenbelt beyond the GLA boundary. This huge housing capacity could effectively solve London and the South East’s housing crisis. So is developing on the greenbelt the answer?

Opportunities for new housing on London greenbelt land, Centre for Cities Delivering Change Report 2014.

Usable Land and the Value of the GreenbeltThe gigantic housing development capacity figures quoted in the Centre for Cities report certainly demand attention. As housing development is such a central issue for planning in the South East, I have decided to repeat the Centre for Cities spatial analysis from a sustainable urbanism perspective and assess how realistic these recommendations are, and what the environmental consequences of the greenbelt development approach are likely to be.

First of all, some details on the Centre for Cities methodology. Their Usable Land definition is a 2km crow-flies buffer of rail and underground stations, excluding several environmental protection area types (SSSIs, AONB, SAC, SPA, Ancient Woodlands). The report does not argue that all this land should be developed, rather that it could be considered for development on a case by case basis. They take a ballpark figure that, given infrastructure, services and removing highly amenable land, 60% of the remaining land could be developed for housing at an overall average of 40 dwellings per hectare (thus each hectare of usable land effectively translates to 24 homes). I have repeated this method below and I get a very similar result of 120,000 hectares / 2.87 million homes on London greenbelt land beyond the GLA boundary. I get a lower (but still substantial) figure of 12,700 hectares / 306,000 homes on greenbelt land within the GLA.

There are two main spatial analysis issues with the Centre for Cities method of identifying usable land- firstly there are significant development restrictions missing, and secondly there are problems with using rail station buffers as a proxy for sustainable travel. Regarding the first problem, the most significant restrictions that should be included are flood risk areas, and additional environmental land and habitats (principally Priority Habitat Areas). The impact of these additional restrictions is shown in the map below. Surface water and flooding risk in particular covers large areas of land in the Thames Valley west of the GLA, and north in the Lee Valley, reflecting the role of the greenbelt in flood management. Assuming these areas would not be developed, this removes nearly 40% of the usable land from the analysis, leaving 75,000 hectares. With more data and time, further restrictions could be considered, for example local site access, road congestion, airport flight paths, heritage restrictions etc.

The second problem is how to consider public transport accessibility and sustainable travel. The basic principal used by Centre for Cities is sound- directing development to areas of public transport access. But locations within 2km of rail stations in the South East are often very small towns and villages, lacking local retail and services opportunities. Not surprisingly these small towns are generally highly car dependent, with around 80% of commuters driving to work, and similar patterns for other trip purposes. Building further low density housing in these locations would likely reproduce this pattern of car dependence.

Ideally the appropriate method here would be to do some accessibility modelling and network analysis (comparable to the PTAL approach used in the London Plan) to identify locations with access to local services and a range of public transport options. Unfortunately performing accessibility modelling for the whole of the South East is not trivial. The maps below shows a simpler alternative, identifying locations within an estimated local walk/bus trip of a retail and service centre (3km of a large centre, 2km of a medium centre or 1km of a small centre) based on 2010 Valuation Office data, in addition to the 2km buffer of rail stations. It is clear that a stricter definition of accessible locations greatly reduces the resulting volume of usable land, directing potential development to larger settlements with more facilities (and public transport services) like Southend, Maidstone and Hemel Hempstead. In this case it leaves 27,500 hectares of greenbelt land beyond the GLA, or 23% of the original figure. Note we also haven’t considered public transport capacity, which is a critical issue for commuters into London as many services are overcrowded.

This analysis points to the Centre for Cities figure of 3 million potential homes in the greenbelt being a big overestimate if sustainable planning guidance is going to be followed. Yet even with this stricter approach I still get a large figure of 27,500 hectares of potential development land in the greenbelt beyond the GLA, which would be about 650,000 homes at suburban densities or more at higher densities. This could go a long way to alleviating the housing crisis in the South East. The Centre for Cities report is convincing in its wider policy argument that land should be ‘evaluated on its merits’ rather than being fixed by blanket restrictions. Greenbelt development could play an important and perhaps even relatively sustainable role in addressing the housing crisis.

The question then is how any release of greenbelt land can be managed to prevent sprawl and retain the many environmental roles that the greenbelt embodies. There is also the problem of making the case to the public when the greenbelt has traditionally been a popular policy. And so we come back to the issue of local authorities cooperating to tackle regional challenges. A million commuters cross the GLA boundary every weekday, yet regional planning is almost non-existent. Any release of greenbelt land needs to be considered in its regional context and balanced against brownfield opportunities. The biggest housing opportunities are linked to new infrastructure (e.g. Crossrail both West and East of the GLA; the Varsity Line for Oxford-Milton Keynes-Cambridge), again at the regional scale. Its hard to see how the housing crisis can be tackled without much greater regional cooperation and some form of regional planning for the South East.